1. Field of Invention
The present invention relates to the reduction of residual styrene from a thermoset resin and, more particularly, to a styrene polymerization agent in aqueous environments that effectively and economically reduces styrene emissions and effluents in moist environments.
2. Description of the Prior Art
The composites industry today is experiencing significant growth as an ever-increasing number of industry applications are being found for reinforced plastics. This is largely owing to the durability, strength, cost and expected lifetime of such plastics. One application in particular is the Cured-In-Place Pipe (CIPP) industry, in which piping systems are repaired through the application of resin compounds to damaged pipe surfaces while the pipes remain buried underground. Underground pipes are used for the transport of petroleum, natural gas, chemicals, municipal water, and the like. Due to exposure to a number of influences over time such as, for example, temperature fluctuations, ground movements, corrosive fluids, etc., these pipes tend to crack and damage. As a result, the pipes often are unable to successfully transport the above mentioned fluids and thus become unsuitable for their intended use. The Cured-In-Place Pipe (CIPP) method for repair can solve this problem without expensive excavation. For example, U.S. Pat. No. 4,009,063 by Wood issued Feb. 22, 1977 shows a method of lining pipe with a hard, rigid pipe of thermosetting resin using a tubular fibrous felt immersed in the resin to form a carrier for the resin. The immersed felt and resin are expanded by an inflatable tube to shape the resin to the passageway surface until the resin is cured to form a hard, rigid lining pipe with the felt embedded therein. The resin is a thermosetting resin which contains a catalyst, and hot air, water, a combination of air and water or ultraviolet light (UV) is used to activate the catalyst or UV initiator causing the resin to cure and form a rigid liner.
Another approach involves utilizing glass fiber which is woven into a tubular shape. The glass fiber is impregnated with a thermosetting resin containing a catalyst, and the resin is then cured. Carbon fiber may be interwoven with the glass fiber such that curing may be accomplished by applying an electrical current to the carbon fibers to generate heat. As a result, the catalyst is activated and the resin cures forming a rigid pipe lining. In this instance, hot air or hot water is not required.
There are still other methods that rely on UV curing. In all such cases the higher temperature or light provides the energy to cure the thermosetting resin, causing it to harden into a structurally sound, jointless pipe-within-a-pipe. Unfortunately, during the curing process, the curing water/condensate becomes contaminated with styrene that has permeated through the film coating material. Indeed, the leaching of styrene through the coating material is apparent as an oily substance on the coating even prior to installation. This poses grave environmental health concerns for air emissions as well as process effluents released downstream, into treatment plants, or in the case of storm sewer rehabilitation: streams, rivers, lakes, public and private water supplies. During the process, employee and public safety is at risk.
Employee exposure is tightly regulated by an Occupational Safety and Health Administration (OSHA) workplace airborne threshold limit value (TLV) of 50 parts per million (ppm) in many states. Releases to the air are regulated by the Clean Air Act (CAA) National Emission Standards for Hazardous Air Pollutants (NESHAP) for plastic composites and boat manufacturing. Releases to the water are regulated by the Clean Water Act (CWA). The Environmental Protection Agency (EPA) and the local Department of Environmental Protection (DEP) agencies have styrene listed as a reportable hazardous chemical. California has listed styrene as a carcinogen. Other states have styrene listed as a possible carcinogen and a marine pollutant. Compliance to regulating authorities can only be met by cost-effectively implementing pollution preventive methods and technologies that reduce toxic and hazardous emissions.
The problem is highlighted in the following article: “Odour Control—More than Sewage when Installing Cured-In-Place Pipe Liners”, NASTT No-Dig, March 2004, Gerry Bauer, P. Eng. & David McCartney, P. Eng, City of Ottawa. The City of Ottawa Canada identified five sections of sewer for rehabilitation by a cured-in-place pipe methods. The contract was tendered, but during lining of the initial sections, numerous complaints were received from the public regarding an unpleasant odor in their homes. Investigations revealed that the odor complaints occurred as a result of styrene. The solution mentioned in this report was to dilute the air concentration with equipment, fans above a manhole. Regulatory agencies require reduction at the source means and not by dilution. No testing on the release water was implemented.
Another problem highlighting Cured-In-Place Pipe emissions is: “Fumes From Va. Sewer Work Cited In Illnesses”, Washington Post Staff Writer, Annie Gowen, May 12, 2004, Page B08. The residents of the Warwick Village neighborhood of Alexandria, Va. were affected by styrene fumes from a CIPP application to their sanitary sewer system. High concentrations were reported on hoses used in the operation, no testing from the source have been reported.
Yet another problem where health officials were called in to investigate, Schlitz Park Office Building, Milwaukee County, Wis. Styrene fumes entered the building through drains and foundation walls. Employees were evacuated and some missed work for months. Fans were used to create airflow to dilute concentrations of styrene. Process water testing at the source was not part of the investigation.
“Styrene is a common chemical component used in rubber and plastics industries to make packaging, insulation and fiberglass products. It is also associated with combustion processes such as automobile exhaust and cigarette smoke. The odor threshold for styrene has been reported to be 50 parts per billion (Plog 1988). It has been described as having a sweet, sometimes irritant odor. It is slightly soluble in water and is volatile. The most common health effects associated with styrene exposure are mucous membrane irritation and central nervous system effects (e.g. depression, concentration problems, muscle weakness, tiredness, and nausea). Recovery short term effects is typically rapid upon removal from exposure (ATSDR 1992)”. Health Consultation, Schlitz Park Office Building, Wis., Sep. 13, 2005, U.S. Department of Health and Human Services, Agency for Toxic and Disease Registry, Devision Of Health Assessment and Consultation, Atlanta, Ga.
There are conventional styrene reduction strategies including the following:
1. Using low styrene content resins: Although many of these resins are currently available from resin suppliers, this method does not lend to every process, and the physical properties of the final product can be affected. In some instances, the reduction of styrene is not significant enough to make a difference, and in some cases, styrene emissions may even increase.
2. Using controlled spay-on techniques is another method for reducing styrene emissions. This method is very effective and works by controlling the amount of surface area of the wet resin which is exposed to the air, whether spraying gel coat or plain resin.
3. Addition of paraffin wax is another method of reducing styrene emissions. This suppresses styrene emissions through the film it provides but, in doing so, creates the problem of secondary bonding between the laminates which can cause the further delamination of the composite resulting in a structural weakness.
4. Using alternate monomers is a forth method of reducing styrene emissions. Alternate monomers such as methyl methyl methacrylate, vinyl toluene and butyl styrene can be used, or it is possible to use olygomers, which basically consist of two or three molecules that have been combined. They work effectively but can be very expensive and, in addition, some can be more toxic than styrene or made from styrene derivatives, also considered HAP and VOC compounds.
5. Using a closed molding process is another method. This can be extremely effective in lowering styrene emissions, but equipment cost and maintenance cost is a great disadvantage.
6. Using a styrene suppressant is another option.
Further to option 6, a number of styrene suppressant additives are currently available to the composite fabricator. They are most effective when using the open-molding processes and, when properly used, can reduce styrene emissions during the curing stage of the composite. Styrene suppressant agents can effectively and economically reduce styrene emissions when properly used in any open-molding process. Specifically, the advantages of Styrene Reduction in CIPP Cure Water are:                i. No additional equipment needed for as much as a 75% reduction        ii. Minor equipment needed for reductions above 75%        iii. Mixing not required, simply add required amount in water soluble packaging        iv. Non-toxic, Non-Hazardous        v. Meets all compliance regulations        
By way of example, Styrid™ is an existing Styrene suppressant additive manufactured by Specialty Products Company to reduce the amount of styrene vapors escaping from the composites. Styrid™ and most other styrene suppressant formulations contain wax and other components that produce a film on the top of the laminate, creating a barrier which prevents styrene, or organic diluents, from leaving the composite in the form of a vapor during the curing stage. Styrid™ creates a film similar to that provided by paraffin wax.
It would be greatly advantageous to preserve all the above-identified qualities of existing Styrene suppressant formulations and yet provide an even higher level of effectiveness, and worker and public safety, with an advantage to economically reduce HAP and VOC emissions.